Section 1 - Motion And Forces & Conservation Of Energy Flashcards
What do vectors have?
Magnitude and direction
What is distance? Scalar of vector?
Scalar - distance has no specific direction
What is velocity? Scalar or vector?
Vector
What is speed? Scalar or vector?
Scalar
What is displacement? Scalar or vector?
Vector
Explain the difference between scalar and vector quantity
Scalar quantities do not give a specific direction, whereas vector quantities do give a direction
distance travelled =
speed x time
What is the speed of sound in air?
340m/s
What is acceleration?
Acceleration is how quickly you’re speeding up
acceleration =
change in velocity divided by time - (v-u) divided by time
Acceleration due to gravity (g) on Earth =
Roughly 10m/s
What do distance time graphs tell you?
How far something has travelled in a certain amount of time
If the line on a distance time graph is a straight line, what does this mean?
The object has stopped moving
Vertical height = 20m. Horizontal = 2/s. What is the speed?
20/2 = 10m/s
How do you work out the speed if the line is a curve? (Distance time graph)
Draw a tangent to the curve at that point, and then find the gradient of the tangent.
What does a flat line mean on a velocity time graph?
Steady speed
Downhill sections mean what? (Velocity-time graph)
Deceleration
The steeper the graph, the greater the …..?
Acceleration or Deceleration
How do you work out distance travelled on a velocity time graph?
The area under any section of the graph (or all of it) is equal to the distance travelled. Find the value of one square, count the total underneath the line and multiply them together
What is Newton’s first law?
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it’ll carry on moving at the same velocity (same speed and direction)
Acceleration is proportional to the resultant force. True or false?
True
What is Newton’s second law?
F = m x a /
Name 3 safety features in cars that decrease the risk of injuries during large decelerations
Seat belts, air bags (these both slow you down gradually). Crumple zones at the front and back of the car are designed to crumple easily in a collision, increasing the time taken to stop, meaning less acceleration in a short period of time.
What is the difference between weight and mass?
Weight is the force acting on an object due to gravity, whereas mass (a scalar quantity) is just how heavy an object actually is based on how much there is
Weight =
mass (kg) x gravitational field strength (N/kg)
What is the force that keeps something moving in a circle?
Centripetal force
Name a core practical on how to investigate force = mass x acceleration (Newton’s second law)
Motion of a trolley down a ramp. Set up 2 light gates to a data logger, and add mass to the trolley each time. The acceleration should decrease.
What is Newton’s third law?
When two objects interact, the forces they exert on each other are equal and opposite
What is inertia?
Inertia is the tendency for motion to remain unchanged. This means the tendency to keep moving with the same velocity.
How can you work out the inertial mass?
Rearrange Newton’s second law. Change is to m = F/a
How do you work out momentum?
mass (kg) x velocity (m/s)
What is momentum?
Momentum is a property that all moving objects have. It’s defined as the product of the object’s mass and velocity
Total momentum is greater than momentum after. True or false?
False. Total momentum is equal to the momentum after. This is called the CONSERVATION OF MOMENTUM
What does conservation of momentum show?
Newton’s third law
Stopping distance =
Thinking distance + braking distance
What is the thinking distance?
Thinking distance is the distance the car travels in the driver’s reaction time between noticing the hazard and applying the brakes
What is the braking distance?
Braking distance is the distance taken to stop once the brakes have been applied
What is thinking distance affected by?
1) Reaction time - increased by tiredness, alcohol, drugs and distractions (e.g. passengers)
2) Speed - the faster you’re going, the further you’ll travel during your reaction time
What is breaking distance affected by?
1) Speed - the faster you’re going, the longer it takes to stop
2) Mass of the car - a car full of people and luggage won’t stop as quickly as an empty car
3) Condition of the brakes - worn or faulty brakes won’t be able to brake with as much force
4) How much friction is between your tyres and the road -you’re more likely to skid if the road is dirty, if it’s icy or wet or if the tyres are bald (tyres must have a minimum tread depth of 1.6mm)
Name an experiment to measure reaction times
Ruler drop experiment. A ruler is dropped without warning from 0cm and the distance from 0 is measured. The longer the distance, the longer the reaction time.
What is the relationship between braking distance and speed?
Squared relationship. If the speed doubles, the braking distance would increase by a factor of 4 (2 squared)
What are the eight different energy stores?
1) Kinetic
2) Thermal
3) Chemical
4) Gravitational potential
5) Elastic potential
6) Electrostatic
7) Magnetic
8) Nuclear
What type of energy does a moving object have?
Kinetic energy - every moving object uses kinetic energy
Kinetic energy =
1/2 x mass x (speed)2
What is energy measured in?
Joules (J) - capital J
What type of energy does an object at a height have?
Gravitational potential energy (GPE)
Gravitational potential energy =
mass x gravitational field strength x change in vertical height
What does conservation of energy mean?
Energy is never created or destroyed
Name the four main ways to transfer energy
1) Mechanically - a force acting on an object e.g. pushing, stretching, squashing
2) Electrically - a charge of doing work against resistance e.g. charges moving round a circuit
3) By heating - energy transferred from a hotter object to a cooler object e.g. heating a pan on a hob
4) By radiation - energy transferred by waves e.g. energy from the Sun reaching Earth by light
What type of energy transfer is a ball rolling up a slope?
Mechanically. The ball does work against gravitational force, so it is transferred from the kinetic energy store of the ball to its gravitational potential energy store
What type of energy transfer is a kettle boiling water?
Electrically. Energy is transferred electrically from the mains to the heating element of the kettle, and then by heating to the thermal energy store of the water
When is energy useful?
When it is transferred from one store to a useful store
The less energy wasted, the more efficient the device. True or false?
True
Efficiency =
Useful energy transferred by device (J)
(divided by)
Total energy supplied to the device (J
Energy is never wasted in a device. True or false?
False. Some energy is always wasted in a device, and it is normally thermal energy. The efficiency can never be equal to or higher than 1 (or 100%)
What is the name of the diagrams that show the efficiency of a device?
Sankey diagrams
Name two ways of reducing energy transferred
1) Lubrication - reduces the energy transferred by friction. This transfers energy mechanically (work is done against friction) to the thermal energy store of the objects involved, which is then dissipated by heating to the surroundings.
2) Insulation - reduces the rate of energy transfer by heating. When one side of an object is heated, the particles in the hotter part vibrate more and collide with each other. This transfers energy from their kinetic energy stores to other particles, which then vibrate faster. This is called conduction.
What are non-renewable energy resources?
Non-renewable energy resources are fossil fuels (coal, oil, gas) and nuclear fuel (uranium and plutonium)
Will coal, gas, oil and nuclear fuels ever run out?
Yes. Fossil fuels are natural resources that form underground over millions of years that are typically burnt to provide energy.
Name 2 advantages of burning fossil fuels and nuclear fuels
1) Fossil and nuclear fuels are reliable. There is still plenty of fuel to meet current demands, and power plants always have fuel in stock.
2) The cost to extract fossil fuels is low, and power plants to burn them are relatively cheap to build and run.
Name 2 disadvantages of burning fossil fuels and nuclear fuels
1) Nuclear power plants are pretty costly to build, and to safely decommission
2) They create environmental problems. Fossil fuels release carbon dioxide (CO2) into the atmosphere when they’re burned, which adds to the greenhouse effect, and contributes to global warming. Burning them can also release sulfur dioxide, which causes acid rain.
Name 5 renewable energy sources
1) Bio-fuels
2) Wind
3) The Sun (solar)
4) Hydro-electricity
5) Tidal
What are bio-fuels? Advantages and disadvantages?
Bio-fuels are made from plants and waste. They can be solids, liquids or gases, and can be burnt to produce electricity or run cars in the same way as fossil fuels. However, the cost if very high to use bio-fuels
What is wind power? Advantages and disadvantages?
Wind power is made by using wind turbines. Each turbine has a generator inside it - the wind rotates the blades which turn the generator and produce electricity. There is no pollution. Initial running costs are high, but running costs are minimal. However, they can be unreliable in places or times of the year when there is little wind. It will sometimes fail to meet demands
What is solar power? Advantages and disadvantages?
Solar power comes from the sun using solar panels, and solar cells are made from materials that use energy transferred by light to create an electrical current. Solar power is often used in places where it is generally the only option (e.g. Australia). Initial costs are high, but there are virtually no running costs.
What is hydro-electricity? Advantages and disadvantages?
Producing hydro-electricity usually involves flooding a valley by building a big dam. Rainwater is caught and allowed out through turbines. There is no pollution. It has a big impact on the environment due to the flooding of the valley and potential loss of habitats. Initial costs are often high, but there are minimal running costs and is generally a reliable energy source.
What is tidal power? Advantages and disadvantages?
Tidal power is generated using big dams that are built across river estuaries with turbines in them. As the tide comes in it fills up the estuary. The water is then let out through turbines at a controlled speed to generate electricity. There is no pollution, but they affect boat access and can spoil the view . However, they are pretty reliable (they always happen twice a day), but the height of the tides is variable and barrages do not work when water level is the same either side. Initial costs are moderate, but there are no fuel costs and minimal running costs.
Why does the UK plan to use more renewable energy resources in the future?
Because of the UK’s growing population, the demand for fossil fuels would become higher, meaning more pollution. The UK’s electricity use has been slowly decreasing, as we get better at making appliances more efficient. The UK aims to use renewable energy resources to provide 15% of its total yearly energy by 2020.
